Musculoskeletal pain is one of the most common illnesses among the people in NE Thailand which is commonly treated by self-medication. Ya-chud (several medicines together in a small plastic bag) for the treatment of musculoskeletal pain is an illegal treatment but has been used by lay people for more than 20 years. A better understanding of the people's perception of and behaviour in taking Ya-chud for treatment of musculoskeletal pain should help in designing an effective implementation programme to reduce the taking ofYa-chud. The study group was 15 years old and over and lived in 2 rural (N = 619) and 2 urban (N = 494) areas of NE Thailand. The study method used individual interviewing. The study aimed to investigate self-treatment of musculoskeletal pain with and without Ya-chud in the urban and rural areas. The attitudes of Ya-chud users in the urban (N = 136) and the rural (N = 128) were measured using a 6 point Likert Scale with a Conbach's alpha coefficient of 0.7509. Comparative analyses of variables between these two areas and between the users and non-users were conducted. Indepth interviews and laboratory analysis of Ya-chud samples were carried out to obtain more detailed information. The study found that Ya-chud for musculoskeletal pain was often used as the alternative treatment to treat pain which occurred at many locations of the body at the same time when the previous outcome had been unsatisfactory. The discriminant stepwise analysis showed that 85.9 percent of Ya-chud users in both rural and urban areas were 25 years old and over and had an education level of primary/secondary school. The overall prevalence of Ya-chud users in the rural areas was higher than in the urban areas but the prevalence of those who had taken Ya-chud within one year was greater in the urban areas. Ya-chud use varied with the season. It peaked during periods of heavy work such as harvesting. The main source of Ya-chud was groceries (82.3 percent in the urban and 79.6 percent in the rural). People had the perception that Ya-chud was a potent drug, cheap and had beneficial effects. They also perceived that the specific name of Ya-chud was easy to remember and described their symptoms. Attitudes towards Ya-chud were positive in the rural areas but negative in the urban areas (p < 0.01). Most of the respondents did not know the harmful effects of Ya-chud. The study showed that the locations of pain for nonusers were not different from the users and also that the treatment outcome after taking Ya-chud was predominantly 'no change' (46.2 percent in the rural and 44.6 . percent in the urban) (p < 0.01). The results from the Ya-chud users in-depth interviews indicated that in the urban areas there was more use of massage, rest and health services for the treatment of musculoskeletal pain but in the rural areas medicines from the drug stores were more often used (p < 0.01). Only 10.9 percent of the respondents could be cured by the above treatments in the urban areas and 4.4 percent in the rural areas (p > 0.05). After taking Ya-chud the result of treatment was a 'cure' for 45.5 percent of users in the urban and for 35.3 percent of users in the rural areas (p > 0.05). Identification of the medicines contained in a packet showed that steroids, NSAIDs and tranquillisers were most often combined in a package. It can be concluded that Ya-chud for musculoskeletal pain is not only unnecessary but also a dangerous use of these hazardous medicines which mask the symptoms rather than cure the illness. Intensive and continuous education campaigns together with legal enforcement should be beneficial for a short term programme to reduce Ya-chud use. Long term programmes should focus on providing licensed dispensers in every drug store so that the lay people can gain more helpful knowledge about medicines and so that legal enforcement can be better implemented since pressure could then be brought to ensure such licensed dispensers complied with legislation.